Predators structure many ecological communities through their inducible behavioral defenses on prey. Much is known about prey responses to conspecific chemical cues, but less is known about how prey respond to heterospecific cues. We tested for prey behavioral responses to cues from a predator (top predator) fed conspecific prey and a heterospecific prey that was also a predator of the focal prey species (intermediate predator). The study was conducted in aquaria with a simple food web of physid snails as the focal prey, damselfly larvae as the heterospecific prey, and giant water bugs as the predator. We used five treatments to separate how chemical cues emitted from the predator fed conspecifics and heterospecifics, as well as chemical cues from injured snails, alarm cues, affected snail behavior.
Results/Conclusions
Giant water bugs that were fed damselfly larvae induced the strongest anti-predator response in snails resulting in the greatest number of snails moving above the waterline. Snails also moved out of the water in response to conspecific chemical cues. Snails responded similarly if they were fed chemical cues or injured snails. These results suggest that intermediate predators provide reliable information on threats of predation to shared prey.